VulnerabilityDeferred

CVE-2025-40297

In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix use-after-free due to MST port state bypass syzbot reported[1] a use-after-free when deleting an expired fdb.

HIGH 7.8EPSS 0.16%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.16%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix use-after-free due to MST port state bypass syzbot reported[1] a use-after-free when deleting an expired fdb. It is due to a race condition between learning still happening and a port being deleted, after all its fdbs have been flushed. The port's state has been toggled to disabled so no learning should happen at that time, but if we have MST enabled, it will bypass the port's state, that together with VLAN filtering disabled can lead to fdb learning at a time when it shouldn't happen while the port is being deleted. VLAN filtering must be disabled because we flush the port VLANs when it's being deleted which will stop learning. This fix adds a check for the port's vlan group which is initialized to NULL when the port is getting deleted, that avoids the port state bypass. When MST is enabled there would be a minimal new overhead in the fast-path because the port's vlan group pointer is cache-hot. [1] https://syzkaller.appspot.com/bug?extid=dd280197f0f7ab3917be

CVSS 3.1: 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.16% probability · 5th percentile
CISA KEV: Not listed
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.